SEGMENT INFORMATION - Details of Segment Information - Statement of Financial Condition (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Cash and cash equivalents	$ 647,812	$ 620,757	$ 711,089	$ 723,866
Goodwill	475,493	166,007
Other segment assets	11,061,112	6,462,106
Total assets	12,184,417	7,248,870
Capital expenditures	3,688	5,498
WSFS Bank
Segment Reporting Information [Line Items]
Cash and cash equivalents	178,195	115,147
Goodwill	455,294	145,808
Other segment assets	10,831,733	6,225,820
Total assets	11,465,222	6,486,775
Capital expenditures	3,669	4,779
Cash Connect
Segment Reporting Information [Line Items]
Cash and cash equivalents	462,345	491,863
Goodwill	0	0
Other segment assets	6,469	7,743
Total assets	468,814	499,606
Capital expenditures	11	375
Wealth Management
Segment Reporting Information [Line Items]
Cash and cash equivalents	7,272	13,747
Goodwill	20,199	20,199
Other segment assets	222,910	228,543
Total assets	250,381	262,489
Capital expenditures	$ 8	$ 344